1. Field of the Invention
The present invention generally relates to apparatuses for recording and regenerating data, and more particularly to an apparatus for recording and regenerating data, which apparatus can reduce data regeneration errors caused by a defect of a recording medium or waveform interference between data indicated by a regenerative signal and improve a data generation rate.
Also, the present invention relates to the apparatus for recording and regenerating data which apparatus can eliminate low-frequency noise and high-frequency noise included in a regenerative signal of recorded data and then regenerate the recorded data.
2. Description of the Related Art
Recently, there are many kinds of apparatuses for recording data such as a magnetic disk, a magnetic tape, an optical disk, a magneto-optical disk or the like. A magnetic recording mark is mainly used to record data to these apparatuses. These apparatuses can permanently maintains data more than a semiconductor memory. Thus, since a large amount of data is currently required to process, these apparatus for computers are essential to record graphics and image data for computers.
In a conventional data recording apparatus, data are recorded in accordance with a predetermined format. FIG. 1 is a diagram showing a conventional data format. In the conventional data format, data or data blocks are recorded simultaneously while a VFO area for an AGC (Automatic Gain Control) adjustment and a PLL (Phase-Locked Loop), a Sync-pattern indicating a start of data, or a Resync-pattern for re-synchronizing is inserted. In FIG. 1, these patterns are omitted. In the conventional data recording apparatus, data or data blocks are recorded once on a track or a sector.
FIG. 2 is a diagram showing a conventional circuit configuration for regenerating data recorded in accordance with the data format shown in FIG. 1. In FIG. 2, the conventional circuit configuration is for a most likelihood decode. In the conventional circuit configuration, a BM (Branch Metric) for a sample value 10 obtained by sampling a regenerative signal is calculated at a BM (Branch Metric) calculator 11 and pass metric values are compared at an ACS (Add-Compare-Select) 13. Then, selected pass data is sent to a pass memory 14 and also accumulated in a pass metric memory 12 for a next pass metric calculation. In the pass memory 14, a pass merge occurs and then a most likelihood data is output to a DataOUT 15 as a decoded data. It is called a most likelihood detection known as a decoding method that is strong against noise.
However, since a data recording technology has been developed quickly to record data at higher density, a signal to noise ratio (SNR) is deteriorated by data recorded at higher density. Thus, the data recorded at higher density can not be properly decoded by the conventional most likelihood detection.
Thus, it is desired to improve a regeneration performance for the data recorded at higher density.